Cell Biology & Neurobiology Lecture Notes Flashcards

Alpha helix

Spiral protein structure whose hydrophobic side chains frequency cover the lipid bilayer

Amphipathic

molecular property having both hydrophilic and hydrophobic regions (like the lipid bilayer)

Beta barrel

rolled up beta-sheet structure forming a rigid cylinder across a membrane to allow solute passage

Cell cortex

specialized network of structural proteins attached to the cystolic side of the plasma membrane

Cholesterol

rigid steroid molecule in animal membranes that buffers membrane fluidity against temperature changes

Fatty acid

a molecule with a long hydrocarbon tail attached to a carboxyl group used as a building block for lipids

Flip-flop

rare tansfer of a lipid molecule from one leaflet of a bilayer to the opposite leaflet

Flippases

ATP-driven enzymes that selectively move specific phospholipids to the cytsolic leaflet to maintain asymmetry

Glycocalyx

a carbohydrate-rich protective layer on the exterior surface of the plasma membrane

Glycolipids

lipids attached with carbohydrates found on the extracellular surface helping with cell recognition

Glycoprotein

membrane proteins with short oligosaccharide chains attached to its polypeptide chain

Hydrophilic

Water loving; molecular property describing affinity for water due to polarity or charge

Hydrophobic

Water fearing; molecular property describing exclusion from water due to nonpolar character

Inositol phospholipid

a minor membrane phospholipid that plays a crucial role in intracellular signaling pathways

Integral membrane protein

protein directly attached to or embedded within the lipid bilayer; needs detergents to extract (includes transmembrane proteins)

Lectin

cell-surface or extracellular protein that specifically binds to carbohydrate structures

Peripheral protein

protein bound non-covalently to the membrane surface without embedding in the hydrophobic core

Phospholipids

primary amphipathic lipid component of cell membranes with a phosphate head and two fatty acid tails

Porin

large pore-forming beta-barrel protein in outer membranes allowing passive passage of small molecules

Proteoglycan

a heavily glycosylated protein contributing to the extracellular matrix and glycocalyx

Saturated

a fatty acid chain containing only single C-C bonds, making the membrane less fluid

Scramblase

membrane enzymes that catalyze the random transfer of phospholipids between bilayer leaflets; flip lipids back and forth between both leaflets of lipid bilayer (scrambling them)

Spectrin

flexible fibrous protein of the red blood cell cortex that maintains cell shape

Tight junction

a cell-cell junction that seals neighboring epithelial cells to prevent leakage

Unsaturated

fatty acid chain with one or more double bonds that creates kinks to increase fluidity

Active transport

movement of solutes across a membrane AGAINST their CONCENTRATION GRADIENT requiring energy

Antiport

a coupled transporter that moves two different solutes across the membrane in OPPOSITE directions

Aquaporin

a specialized channel protein that selectively facilitates the rapid passage of water molecules

Calcium pump

an active transport pump using ATP to clear Ca2+ out of the cytosol into the extracellular or ER spaces; AGAINST CONCENTRATION GRADIENT

Channel

transmembrane protein forming a hydrophilic pore that allows PASSIVE DIFFUSION of speicfic ions or molecules

Electrochemical gradient

combined driving force of concentration difference and electrical charge across a membrane

Glucose transporter

uniporter protein that carries glucose across the membrane by PASSIVE FACILITATED DIFFUSION

Membrane potential

difference in electrical charge across a cell’s plasma membrane

Osmosis

PASSIVE water movemnt across a membrane in response to solute concentration gradients

Passive transport

movement of solutes across a membrane DOWN their CONCENTRATION GRADIENT without energy

Pump

ACTIVE transporter that uses metabolic energy to move solutes AGAINST their gradient

Sodium-glucose symport

a co-transporter using the downhill Na+ gradient to pull glucose into the cell AGAINST its gradient

Sodium-potassium pump

primary ACTIVE transporter that pumps 3 Na+ OUT and 2 K+ IN using ATP

Symport

a coupled transporter that moves 2 DIFFERENT solutes across the membrane in the SAME direction

Transport

the movement of ions, small molecules, or macromolecules across a cellular membrane

Uniport

Carrier protein that transports a SINGLE type of solute across the membrane in ONE direction.

Auditory hair cells

Specialized sensory receptor cells in the inner ear (cochlea) that convert mechanical sound vibrations into electrical neural signals.

Basilar membrane

flexible membrane in the cochlea that vibrates in response to sound waves

K+ leak channels

ion channels that remain continuously open to allow potassium to exit; sets the resting potential

Ligand-gated

channel that opens ONLY when a specific signaling molecule binds to it

Mechanically-gated

channel that opens in response to physical forces such as stretch or pressure

Selectivity filter

structural feature of ion channels that ensures ONLY specific ions can pass through

Stereocilia

microscopic projection on hair cells whose mechanical bending opens ion channels

Tectorial membrane

gel-like structure in the cochlea agianst which hair cell stereocilia deflect

Voltage-gated

a channel that opens or closes in response to changes in membrane potential

Acetylcholine

major excitatory neurotransmitter involved in muscle stimulation and central nervous system signaling

Action potential

rapid, self-propagating electrical reversal across a cell membrane used to transmit signals

Channelrhodopsin

a light-activated cation channel used to induce action potentials with blue light; isolated from green algae which causes sodium influx and fires instant AP

Depolarization

shift in membrane potential toward a less negative value

Dendrite

branched neuronal extension that RECEIVES synaptic input from other neurons

GABA

primary INHIBITORY neurotransmitter in the adult central nervous system; hyperpolarizes target neurons to prevent over-excitation (stroke)

Glutamate

primary EXCITATORY neurotransmitter in the central nervous system; triggers depolarizations

Glycine

INHIBITORY neurotransmitter primarily active in spinal cord and brainstem; opens chloride channels to dampen neuronal firing; achiral amino acid

Nerve impulse

propagated action potential traveling along a neuron to transmit information

Neurotransmitter

chemical signaling molecule released across the synaptic cleft to bind postsynaptic receptors

Optogenetics

technique using light-sensitive proteins to control neuronal activity with light

Synapse

specialized functional junction where a signal passes from neuron to a target cell

Synaptic cleft

narrow fluid-filled extracellular space separating presynaptic and postsynaptic cells

Transmitter-gated ion channel

a postsynaptic receptor channel that opens DIRECTLY UPON binding to a neurotransmitter

Voltage-gated calcium channel

axon terminal channels opening DURING depolarization to trigger neurotransmitter exocytosis

Voltage-gated potassium channel

channels that open with a slight durig during an action potential to repolarize the membrane

Voltage-gated sodium channel

transmembrane channels opening rapidly during depolarization to allow Na+ influx during an action potential

Uniport vs Symport

Similarity: both are membrane transport proteins that SELECTIVELY carry solutes across the lipid bilayer

Difference: uniport only carries 1 solute down its concentration gradient, whereas symport co-transports 2 different solutes in the same direction simulataneously

Pump vs Transporter

Similarity: both bind specific solute molecules and undergo sequential conformational changes to move solutes across the membrane

Difference: pumps require metabolic energy (ATP or light) to move solutes AGAINST their electrochemical gradient, whereas passive transporters do not requre energy and move solutes DOWN their gradient

Ligand-gated vs Voltage-gated Channel

Similarity: both form hydrophilic membrane pores that open to allow rapid, passive diffusion of specific ions down their electrochemical gradients

Difference: ligand-gated chanenls open in response to the BINDING of a specific chemical signal (like a neurotransmitter), whereas voltage-gated channels open in response to SHIFTS in the electric membrane potential

Phospholipids vs Glycolipids

Similarity: both are amphipathic lipid molecules containing hydrophobic fatty acid tails that help form biological membranes

Difference: phospholipids have phosphate-containing polar head group, while glycolipids have covalently attached carbohydrate/sugar groups on the extracellular leaflet

Optogenetics vs Voltage-gated Sodium Channel

Similarity: both modulate neuronal excitability by allowing ion flux across the plasma membrane to alter membrane potential

Difference: optogenetics uses artifically engineered, light-sensitive proteins (like channelrhodopsin) controlled by external light, whereas voltage-gated sodium channels are naturally occuring channels activated by membrane depolarization